export function debounce(func, wait, immediate) {
  let timeout, args, context, timestamp, result;

  const later = function() {
    // 据上一次触发时间间隔
    const last = +new Date() - timestamp;

    // 上次被包装函数被调用时间间隔 last 小于设定时间间隔 wait
    if (last < wait && last > 0) {
      timeout = setTimeout(later, wait - last);
    } else {
      timeout = null;
      // 如果设定为immediate===true，因为开始边界已经调用过了此处无需调用
      if (!immediate) {
        result = func.apply(context, args);
        if (!timeout) context = args = null;
      }
    }
  };

  return function(...args) {
    context = this;
    timestamp = +new Date();
    const callNow = immediate && !timeout;
    // 如果延时不存在，重新设定延时
    if (!timeout) timeout = setTimeout(later, wait);
    if (callNow) {
      result = func.apply(context, args);
      context = args = null;
    }

    return result;
  };
}

export const isMobile = () => {
  const userAgentInfo = navigator.userAgent;  
  return /Mobile/i.test(userAgentInfo);
  // const mobileAgents = ["Android", "iPhone", "SymbianOS", "Windows Phone", "iPad", "iPod"];
  // const mobileFlag = mobileAgents.some((mobileAgent) => {
  //   return userAgentInfo.indexOf(mobileAgent) > 0;
  // });
  // return mobileFlag;

  // let ua = navigator.userAgent,
  // isWindowsPhone = /(?:Windows Phone)/.test(ua),
  // isSymbian = /(?:SymbianOS)/.test(ua) || isWindowsPhone,
  // isAndroid = /(?:Android)/.test(ua),
  // isFireFox = /(?:Firefox)/.test(ua),
  // isChrome = /(?:Chrome|CriOS)/.test(ua),
  // isTablet = /(?:iPad|PlayBook)/.test(ua) || (isAndroid && !/(?:Mobile)/.test(ua)) || (isFireFox && /(?:Tablet)/.test(ua)),
  // isPhone = /(?:iPhone)/.test(ua) && !isTablet,
  // isPc = !isPhone && !isAndroid && !isSymbian;
  // return {
  //   isTablet: isTablet,
  //   isPhone: isPhone,
  //   isAndroid: isAndroid,
  //   isPc: isPc
  // };
}

export const isExternal = (path) => {
  return /^(https?:|mailto:|tel:)/.test(path);
}
